1. Field of the Invention
The present invention relates to a dry pipe/deluge valve for automatic fire protection sprinkler systems, and in particular a hydraulically-operated valve for use as a primary control valve in a dry pilot, deluge, preaction, or other special types of fire protection systems.
2. Related Art
A conventional fire protection system includes automatic sprinklers connected to a conduit to receive pressurized fire-extinguishing fluid, such as water. Such systems are referred to as “wet pipe” systems. A typical sprinkler has a base with a threaded portion for connection to the conduit and an output orifice to output the fluid to provide fire control and/or suppression. The output orifice is sealed by a seal cap, which is held in place by a release mechanism. The release mechanism is designed to release the cap under predetermined conditions, thereby initiating the flow of fire-extinguishing fluid. A typical release mechanism includes a thermally-responsive element, e.g., a frangible bulb or fusible link, and may also include a latching mechanism.
Certain fire protection systems have a central valve, referred to as a “dry pipe valve” or “deluge valve,” that controls the flow of fire extinguishing fluid from a high pressure supply input to a system output connected to the sprinkler conduits. A typical dry pipe valve has a main chamber for controlling fluid flow from the supply input to the system output. The valve also has a secondary, i.e., “sensing” chamber, to which a fluid-based control line is connected. The valve maintains a balance (i.e., a pressure differential) between the pressure in the sensing chamber and the pressure in the fluid supply input line, which is sealed with a cover (referred to as a “clapper”) in the main chamber. A pressure drop in the sensing chamber below a certain threshold allows the clapper to be forced open by the pressure in the supply line, thereby initiating the flow of fluid through the main chamber to the sprinkler system output.
In dry pipe valve systems, the sprinkler conduits initially act as “pilot” lines, which means that the water in these conduits (in a “wet pilot” system) serves as a means for detecting a fire condition, rather than as a means of extinguishing a fire. In such a system, the pilot lines are connected to the sensing chamber of the dry pipe valve. When a sprinkler is activated under fire conditions, the resulting drop in water pressure in the pilot lines (and sensing chamber) triggers the dry pipe valve to initiate the flow of fire-extinguishing fluid to the sprinklers. The sprinklers on the wet pilot lines (or on a separate set of conduits) then act to extinguish the fire.
A “dry pilot” system may be used in applications in which wet pilot lines are not suitable, such as for refrigerated or sub-freezing storage. Dry pilot systems contain pressurized air or other gases, such as nitrogen, in the conduits connected to the sprinklers, rather than water. When a sprinkler is activated under fire conditions, the resulting drop in air pressure in the pilot lines triggers an actuator (which is usually a separate component from the valve), which in turn releases the water pressure in the sensing chamber. This causes the valve to open, as described above, and initiates the flow of fire-extinguishing fluid to the sprinklers.
Electrically-actuated systems employ a solenoid valve that is triggered by electronic fire or smoke detection devices or other types of electrical control devices. The solenoid may be connected in series with a wet or dry pilot system. For example, in a “preaction” system, a loss of pressure in the pilot lines initiates an alarm, but the system does not open the central valve until the solenoid is electrically-actuated, e.g., by an electrical signal from a smoke detection system. Such systems may be used in sensitive areas, such as computer facilities, in which inadvertent activation of the sprinklers would cause significant damage.